Corrosion Management System of Regional Reinforced Concrete (RC) Bridges

Civil infrastructure assets, including buildings, transportation networks, energy grids and networks, and water-sewer systems, are critical functional components of day-to-day life activity in a modern society. The durability and reliability of these civil infrastructures are largely affected by corrosion-induced structural deterioration. In addition to continual use and increasing traffic demands, natural environmental conditions set degradation due to corrosion damage as a critical condition to durable and reliable infrastructures. Therefore, in order to improve the durability of the bridge infrastructures affected by corrosion in the most efficient manor, we propose a procedure/methodology to manage integrity of corroding RC bridges which is resulted by corrosion assessment by assuming different initial RC systems (including control actions). Our approach involves corrosion characterization in laboratory scale RC samples, quantification of damage based on different corrosion conditions with different corrosion control technologies, and integration of proposed models of the environmental conditions effect on corrosion of RC. Finally, a methodology is included for assessing the component performance and reliability following the performance observed and characterized for different control actions. The corrosion assessment models include deterministic approach and localized probabilistic approach strategies in a system management tool for use by owner agencies in addressing vulnerable structures in aggressive environments. The proposed research consists of three technical tasks and implementations task. The final goal is to validate the methodology with the proposed tools for monitoring and modeling for the corrosion assessment

Preparation and Electrochemical Characterization of Concrete Containing Microencapsulated Calcium Nitrate Corrosion Inhibitor

We present the preparation and inhibition behavior of rebar in the presence of calcium nitrate (CN)-containing microcapsules with concentrations of 0.50, 2.00, and 5.00 wt.% in concrete. From both open circuit potential (OCP) and electrochemical impedance spectroscopy spectra, it was found that an addition of microcapsules containing CN corrosion inhibitor into concrete beams successfully repassivated or maintained the passivity of the rebar when the concrete was cracked. This corrosion inhibitor repassivated the rebar by forming a passive layer on the rebar surface under the crack. This repassivation process was evident by an increase of OCP values to more positive values or by stable OCP values at around -100 mV vs SCE. An increase in phase angle after corrosion activation for the sample with 2.00 wt.% microcapsule clearly showed this repassivation process. The optimum concentration for maintaining the passivity on rebar in the cracked concrete was found to be 5.00 wt.%

The Impedance Reposnse of Different Mechanisms for Li-coo2 /acetylene Carbon Electrodes in Alkaline Solutions under Polarization Conditions

The kinetics of LiCoO2 electrodes with different carbon ratios in alkaline aqueous solutions was studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The composition of the electrode influences the mechanism controlling the interface. The redox reactions identified by CV indicated the potential regions where the charge transfer process is the dominant mechanism. EIS in (Li2SO4 + LiOH) alkaline solutions characterized different interfacial mechanisms when potential bias was applied to electrodes formed with different acetylene carbon (AC)/LiCoO2 ratios. The different carbon/active ratios revealed different interfacial characteristics due to the cylindrical porous distribution of the composite electrode. DC and AC techniques were performed to characterize the interfacial mechanisms influenced by composite ratio, particle geometry and distribution under bias conditions. Transmission line modeling (TLM) was used to characterize the impedance signal resulting from the physical parameters influencing the mechanisms occurring at the porous composite layer/electrolyte interface. Interfacial mechanisms associated with TLM elements helped to quantitatively characterize the functionality of the different LiCoO2/AC ratios present in the electrode compositions. The proposed TL model was validated with the experimental data and high surface characterization, resulting in good agreement

Srb-biofilm Influence in Active Corrosion Sites Formed at Steel-electrolyte Interface When Exposed to Artificial Seawater

Electrochemical evolution of the interface formed by carbon steel exposed to artificial seawater with nutrients in the presence and absence of mixed cultures that contain sulfate-reducing bacteria (SRB) is characterized by electrochemical impedance spectroscopy (EIS). The artificial seawater in sterile conditions progressively covered the surface of the steel sample with two different layers after 30 days of exposure. An outer layer is formed by a mixture of chlorides and phosphorus-based iron corrosion products with organic compounds from the culture media, and an inner layer is formed by corrosion products mixture constituted mainly by phosphorus-base products. Alternatively, under biotic conditions there was one heterogeneous layer composed by a mixture of phosphorous and sulfur-based corrosion products and biofilm. Three time constants were observed with EIS for sterile conditions. At low frequencies one constant is associated with the charge transfer resistance related to the iron dissolution reaction and inversely proportional to the active area; the porous resistance magnitudes at medium frequencies characterized the physicochemical properties of the inner layer, and high frequency described the electrical properties of the outer mixture layer. Low carbon steel in the presence of SRB (halophilic hydrogenotrophic) showed the impedance distribution after the formation of a corrosion product thick black layer mixed with organic composites and bio-entities. The SRB-biofilm enhanced the corrosion rate and influenced the appearance of diffusion controlled mechanism process. Electrical passive analogs in terms of constant phase elements characterized the evolution of the cover films formed and the impedance of the layers with time. The mechanisms are characterized based on the impedance response for three time constants in the absence of SRB and one time constant with a finite Warburg element when SRB are present in the electrolyte. The validation of the theoretical approximation with electrical analogs was in good agreement with the experimental results

Film Properties and Stability Influence on Impedance Distribution During the Dissolution Process of Low-carbon Steel Exposed to Modified Alkaline Sour Environment

In this work, we characterized the anodic dissolution and the hydrogen transport within carbon steel (SAE 1018) samples immersed in alkaline sour solutions (CN−, polysulfide-base inhibitor and H2S(aq)). The evolution of interfacial and transport processes could be quantified by Electrochemical Impedance Spectroscopy (EIS) and hydrogen permeation measurements. EIS experimental data were analyzed and fitted by using Transmission Line Model (TLM); this latter helped to propose the mechanisms through the porous layer of the corrosion products formed. The area influencing the dissolution and the mass transfer process was quantified by the pores number, pores thickness and the interfacial passive electrical elements describing the mechanisms in different regions within the pores of the corrosion product layer. The TLM was used to analyze the active-mass transport processes occurred at different spatial positions of the porous layer, such as the mass transfer at the wall and the active-mass transfer at the base of the cylindrical pore of the non-stoichiometric FexSy